Japanese Laid-Open Patent Application Publication No. 6-273439 discloses a piezoelectric acceleration sensor that detects acceleration from the bend of piezoelectric ceramics. Japanese Laid-Open Patent Application Publication No. 7-140164 discloses a piezoelectric acceleration sensor that simultaneously detects translational acceleration and angular acceleration from the bends of two piezoelectric single-crystal substrates. Japanese Laid-Open Patent Application Publication No. 2000-171480 discloses a piezoelectric acceleration sensor that detects translational acceleration and angular acceleration separately, based on the bends of piezoelectric single-crystal materials and the sign difference between the outputs of the piezoelectric single-crystal materials.
Since two acceleration sensors are used in the conventional technique using piezoelectric ceramics, the low mounting accuracy of the two sensors on a substrate as well as the difference in sensitivity between the two sensors results in poor positioning control. With the acceleration sensor using two piezoelectric single-crystal substrates, there are problems in that a decrease in size is difficult to achieve and angular acceleration and translational acceleration cannot be detected separately from each other. With the acceleration sensor that detects acceleration from the bends of two piezoelectric single-crystal substrates and the sign difference between the two outputs, there are problems in that the production process is complicated and it is difficult to reduce the production cost, because the two piezoelectric substrates are bonded to each other and are then bonded to a supporting substrate.
The object of the present invention is to provide a sensor with a simple structure that eliminates the above problems and can easily detect different types of acceleration, such as angular acceleration and translational acceleration.